Acute Calcific Periarthritis Beyond the Shoulder: A Case Report of Fifth MCP Involvement.

Acute calcific periarthritis (ACP) is a self-limiting periarticular process caused by calcium hydroxyapatite crystal deposition, most commonly affecting the shoulder and rarely involving the hand. We present a case of a 33-year-old woman with acute pain and swelling of the right fifth metacarpophalangeal joint after minor trauma. Radiographs and ultrasonography confirmed periarticular calcification consistent with ACP. The patient was treated with NSAIDs, corticosteroids, and immobilization, resulting in full recovery. This case highlights ACP's diagnostic challenge at atypical sites, where it mimics infection or gout. Recognizing characteristic imaging is essential for accurate diagnosis and effective management.